Sound-reproducer and diaphragm therefor.



D. M. BLISS, SOUND REPRODUCER AND DIAPHRAGM THEREFOR. APPLICATION FILED MAR, 30. 19:7.

.latvnted Nov. 12, 1918.

swag INVEN TOR.

A A TTORNEYS.

DONALD lvi. nrirss, or

"WEST GRANGE,

SOUND-REPELODUCEB AND DIAPHRAGM 'IEIEREEUE.

Specification or Letters Patent.

Patented Nov Application filed March 30, 191?. Serial 1E0. 158,530,

To all whom it may concern;

Be it known that i, DONALD M. Brass, a citizen of th Dominion of Canada, residing at West Grange, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Sound- ;iteproducers and Diaphragms Therct'or, of which the followin is a specification.

My invention relates to )hon0graph or sound reproducers and especially to im proved diaphragins therefor and the manner in which the same are mounted in the soi.md-box.- My preferred diaphragm coinprises a supportingmember ot' flexible material and of high tensile strength, preferably of thin woven fabric, such as finely 'WOVGII silk, which is secured in the casing of the sound-box While stretched nearly to its elastic limit, the predetermined tension to Which this member is subjected being evidenced by the fact that the same has a predetermined tone or pitch when vibrated. A stiffening dist: of less diameter than the. supporting member is secured thereto, this disk havinga omparatively large central opening therethrough substantially in alinement with the neck of the reproducer. This dish is preferably formed of cellular material such as conu'i'resscd paper and is physically stiff relatively to the tensioned su lporting member. A thin disk of high density, relative to that of the stiffening disk just re ferred to, is secured to the diaphragm to cover the central opening therein This central disk p it: ably cupped or concave and the stvlus er is attached thereto. 1 have found it ditlicult; to maintain a uniform tension in the supporting member of the diaphragm when the latter is supported by rings secured to opposite faces of the material. Tlns is because there is a tendency for the supporting rings to collapse at; certain points, unless they are made unusually heavy and rigid. Accordingly, I prefer to secure the supporting member of the diaphragm between a dished plate, which comprises part of the casing of the soundbox. and a ring. Also, preferably, screws are passed through the plate, diaphragm memher and ring and a shell or cover is fitted over the casing. so as to tfOlllPltlCl) cover all oi the scrcw-hczuls and the edges of the plate and ring. therebypreventing acci -lental disturbance f the tension of the diaphragm by tampering with the screws' The above being brief description of prettierred device, it should be under c that my invention is not limited thereto and also that my invention conu'irises certain sub-combinations in addition to the nu. combination of elements. The theor coi'isidcrations on which my invention is based will be more fully disclosed licreiin after. it may, hmvevcr, be brictiv noted, at this point that the eii'ect of the 'tcnsioned and lightsupportiug member oi" the diaphragm,together with the stiffening member secured thereto. is to provide both a tension stitiucss and a physical stiffness to produce a structure which is both resilient and light. Also, by providing in a diaphragm a relatively thick and light member such as the stiffening disk referred to, having a central opening or sound chamber therein, over which is secured a thin member or high density, to which the stylus lever is connected, various advantages accrue. Brictlv.thcovertones and the higher frequency vibrations are well reproduced by the thin central men ber of hifih density, these vibrations not being distributed to any considerable extent in the mass of the larger member to which the thin dense disk is secured. fat the same 'tin'ie. the sine and inertia otthc main portion of -the. diaphragm results in the faithful reproduction of tones of lower pitch in proper balance.

The features just referred to brovide a diaphragm construction having a center ot high density attached to a surrounding area of low sound comluctivit v. The result ol this combination to prevent the tree transmission of sound vibrations from the center of the diaphragm to its pcripbcrvand this I consider a distinct advaut'acjc. Sound vibrations produced in the central disk tend to be reflected back u) their origiuat'ing point from the junction of the cent'ral disk with the Stlll'OtHltlllltI inaticriul of low sound comluctivitv. because of the vcrv dificrcut character oi the conducting medium beyond the junction from that of the medium in which such vibrations orig" inato. iu-cordinglv, it: seems to he the 'case that the high l rcuuenm vibrations which prmlucc the so-called scratch in reproducing from a sound record do not travel beyond the central metal or other high density disk. but are reilcctcd back from the junction of the metal disk with the rest of the diaphragm and so are not distributed through the diaphragm as a whole, but are largely suppressed. At the same time overtones and soprano notes, etc, Which are of an amplitude considerably greater than the scratch vibrations will be reproduced by the central disk which vibrates practically by itself in re 'iroducing the same.

in order that. a clearer understanding of my invention may be had, attention is hcreby directed to the at-coinpanying drawings forming part of this application and illustrating a preferred embodiment of my inventioi'i. 1n the drawings, Figure l repre sents a bottom plan .view of a sound reproducer, Fig. 2 is a section taken. on line .2-9.- of Fig. 1 and Fi 3 is a sectional View of the diaphragm shown in lig. 2 taken on line 22 of Fig. 1.

Referring to the drawings, the casing l of the sound-boxis formed as a metallic disk, somewhat concaved or dished, and having a plane annular surface 2 adjacent its periphery. The diaphragm, of which the supporting member is shown at 3, is secured; between the surface 2 ct plate-l a clamping ring 4. v

The diaphragm, in its preferred form as explained, comprises, in addition to the supporting member 3, a stitiening member or members, shown in the drawing at 5 and 6, and a central member 7 of relatively high density to which is attached the stylus lever 8. This lever carries a stylus 9 and is pivoted in. any usual manner as on centers carr ed by the lugs 16.

The supporting member 3 is formed oi flexible material of high tensile strength and is preferably a disk oi finely woven silk, or other Woven fabric oit high tensile strength. In the production of the dia phragm and reproducer, according; to my preferred method, this fabric first, stretched to about one-half of its elastic limit. This member is maintained under tension through the. various operations. Next, the stiffening disk 5 is cemented to the 'stretchec't fabric, this dish having an axial opening lltherethrough. The me1nher 5 is formed of some material of low sound conductivity, preferably of light character, and of considerable physical stillness in comparison with the supporting member 3. it may be formed of cork, wood, fiber, or other suitable materials, is preferably formed of compressed it is of considerable thickness relative to members 3- and 7. i have illustrated a means of obtaining the desired thicknes which comprises cementing a similar dish 6 to the dish 5, disk 6 being of smaller dis eter than disk 5. This d 6 has a tively large central opening herethrough which may be in substantial alinenient with the neck 13 at the reproducer. has soars 5 N This may taite annulus l7 relt or other suitable mate-- and 6 form, in ff'ect, a sti member having av large central opening 0 sound chamber :lliltl'l therein.

The member con'ipi a snail disk oi rclativc .eriai resilience in cinnparist and 6. The preferred material is resilient metal This nien'iber is preferably a; shed, shown, to increase its and resilienee. it, is secured to the member 5 to cover the central opening through the diaphragin, n'eierably by "en'ienting an an-- nular disk it, which may be termed of strong paper, over the marginal flange oi member 7 and to the s'u' 'nporting inmnber 3. After the metal n'ieniber Y llZl-S.'l)'dc11 cemented in place, the diaphragm ii-hen given. a coating of finishing V51 ish which makes the same. air-tight. ldeinber is then given. a further stretching, nearly to its elastic limit, and while in this stretched condition it secured t the r J llelllbfil 3 is secured between r the edge portion of plate 1 pro cement and additionally by screws 15 bar-- heads 16 on the outer side otplate practice, the final stretcl'iing' of member 3 is accurately determined by comp the tone or pitch oi? the 'n'ier her when vibrated with a standard pitch, the middle C, for e'. :an1ple,'and strwcliing in: char 3 until its tone brought into accordance- With the predetermined pitch.

If desired, a dampen-e may be employed prevent excessive vii ation of member 7. the form, for exan'iple, of an rial interposed between themember 5 and zigthe member 7 adjacent to. the periphery of the concave portion of the latter.

The diaphragm may, o't' eourse, be secured between rings in the usual fashion. if de sired, but I have iiound that it is diilieult to niainto' rin tension with such rings after e di raggn'i has been cut loose from the stretching franc, as there is tendency for the rings to collapse at in points. .io avoid making therln inpraci'jically heavy, therefore, i. find it pr place of one of the rings the arched plate 1 as described, which acts as a closure and sonrid reflecting surface for the sound-box and no vidcs a clamp member which will not buckle. but

is, of course,important tha the tension f the diaphi hould "h t -tore,

means to use in altered after ftl.0

' tional quality of r'eproduet 1- s" of high freqiyenry will vibrate o "311' i '1 u n the edges or the plate and ring, protects ine heads of the screws and gives a finished ZEIYQPQLHEHCQ the reprodueer.

The reproducer described 1r attribn'ied partly in and other sub-combination of the scribed. as comprising my pr" struetion. The use of the dia hers 3 and 5, or 3, 5 and 8 provides a struction in which stillness is produced partly by the physical SilfillQSS of members 5 and 6 and partly by What if may term the tension stiffness of the member 3. The efiicieney of a reprodueer, other i iings bein equal, depends largely upon the lightness, stillness, and resilience of its diaphragm. Such usual diaphragm materials as niioa fiber, or "ah e like have low tensile strengrh and are brittle or l 'i h the structure described. howev r, ihe total resilience or elasticity is greater "zhan t 21* which would he produced by either the stiifening memher or the supporting member a the stiilening member provide inertia and permits the i i should be noted that so arano or o;

the smal tral dla ihramn 'iractioallr ll'lemdl."

b sipation in or through she hea'i phragin of Clll ffilQllt density Nilof deeper tone and grea brats the diaphragnis resilience of the dia same from following the rtjflu; ex

curately, a large perceniiagi of "requencies or" sound vibra 'm not Well reproduced. @n the o ru ns l, diaphragm is made smaller in dianiet li'gsil-iier in weight, the production oihigher frequency been improved the proper balanc between d,

p Y l 3 C Y o I vim l oons roi example in me case or a inane 1.. row);

vantage to so construct a" as to prevent the iree transnns 1 vibrations from the Cfillu to its periphery Sound ":ilirai'zions are largely reflected each point if they a cor.

Wu haraeter ih m seems ii.

a hint;

een'lra sh, in i'he so i but reiierted bani:

Lion or the metal disk with the are largel suppr E l he evident shah one rea' 'ure consists in providing 9. diaconcentric areas of Widel;

v. for Junction of ilection a 1101 l i i sound uonduetivii such areas forming: sound re in'ipeding tic transmission of ins outer edge of the diaphragm.

Will be evident that .nw invention is nor limited to the exact detai s ol the 6011- struciion deserilwih but is as broad as is inilicased by the accompanying; claims.

ii liat claim is: in In a soui'ul-box, a compound diaphragm ooniprisii a relatively thick and ll llil i l a cenlral opening: there irough, supjfiorl'ing member having an aliiied opening and a thin member of hig'l'i density relative to that of the first, secured i'O a face of one of said first members to over l ening' 'zherethrougl'h, suhslanl iiall v as s if. in a so! box. a diaphragm incl! 5 a I r having: a central opening there-- 'l hrougzl and being); formed of cellular lira-- t'irial l'GllilVlY light and l'liie a support ins; in .iber and a third diaphrber serured to one of said other mm 1% d opening. said srond member lieiel thin Ml o l iigh densitr,sub- .3 as sd', forth.

a smmd-box, a diapir ed of dilieren P .1; p arranged eonce 0 her, and being oi ihe contra Y and souno one rounding porrion,

' as set i orlli.

und -bo; a compound diaphragm n'einber having a central openwin a supporting inei'nher a third diaphragm member Se 1 e to cover said first member being of and lower sound conduliirity 1r 1, and

l ass said third member be- ;lienl nieial, substantially as set i a souudliori, a compound diaphragm ilulIlQ; member having a central openll. *hereiihrough. a sup )Dlftlillf member the 1 and a illllCl diaphragm member se-- 12E curse is one of said other members, to cover said opening", said first member being of greater, mass and lower sound conductivity than the third, and said third member b cupped or arched nd of a relatively density and resiliency, substantially as set forth.

I con'iprising 6. In a sound-box, a compound diaphragm a thin flexible supporting member of high tensile strength and elasticity, a physically stiff disk member of less diameter than the supporting member, secured thereto, said disk member and support ing member each having a central opening theretln'ough, and a thin disk of relatively high density secured to one of said members to cover the said opening, substantially as set forth.

7.111 a sound-box, the combination of a casing, a diaphragm-comprising a supporting member of flexiblematerial of high tensile strength, and a physically s tifi member of less diameter secured thereto, means forsecuring said supporting member in the casing under tension, and means for preventing alteration of such tension after the parts have been adjusted, substantially as set forth. I,

8. In a sound reproducer, the combination of a hollow plate, a clamping ring, a diaphragm secured and supported between the edge portion of said plate and said ring, clamping screws extending through the edge portion of said plate and through said diaphragm into said ring, and a casing extending over the outer surface of said plate, inclosing the heads of said screws, and bent to extend around the peripheral edges of the plate and ring, substantially as set forth.

9. In a sound reproducer, the combination of a pair of clamping members, a diaphragmsecured and supported adjacent. its edge between said clamping members, clamping screws extending through one of said mem-- bers and through said diaphragm into the other of said members, and a casing extending over the top surface of the reproducer,

inclosin the heads of said screws, and bent to extenll around the peripheral edges of said pair of clamping members, substantially as set forth.

This specification signed and witnessed this 28th day of March, 1917.

DONALD M. BLISS Witnesses:

DYER SMITH, I. MoIN'rosH. 

